The objective of the proposed research is to determine the potential effectiveness of various enzyme and cellular engineering strategies for the treatment of selected genetic diseases. Trials of replacement therapy by 1) direct enzyme or hormone administration, 2) transplantation of enzyme-producing cells and tissues, and 3) cofactor supplementation to enhance residual enzymatic activities will be evaluated in appropriate cell culture and animal systems prior to clinical trials. These studies will include enzyme therapy for Fabry and Gaucher Type 1 diseases. Normal human splenic alpha-galactosidase A and beta-glucocerebrosidase will be purified and chemically modified to maximize their stabilities and promote their delivery to specific tissues. Endothelial cell culture will provide an in vitro system to evaluate the uptake of alpha-galactosidase A preparations. In vivo replacement strategies will include entrapment in liposomes and autologous erythrocytes; these carriers will be chemically modified to maximize protection and delivery to target sites of pathology. The fate and potential physiologic/immunologic consequences of administered unentrapped and liposome- and erythrocyte-entrapped preparations will be assessed in mammalian model systems. The potential of transplanted, enzyme-producing cells to replace a defective activity will be determined. Viable, isolated hepatocytes from normal mice will be administered intraportally to congenic mice with defective beta-glucuronidase activity; the ability of these hepatocellular allografts to produce normal enzyme will be evaluated. The effect of enzyme therapy by cofactor supplementation will be undertaken in cultured fibroblasts and long-term lymphoblasts from patients with mannosidosis prior to in vivo endeavors; the effect of metal cations on the residual alpha-mannosidase activities and selected substrates will be determined. Clinical trials will be designed to determine the long-term biochemical and clinical effectiveness of each of these therapeutic stategies which may provide new approaches to deliver potent agents for the specific therapy of selected malignant, metabolic, and infectious as well as other genetic diseases.